Method for the construction of impermeable walls

ABSTRACT

A method is disclosed for the construction of an impermeable concrete wall in the ground, the wall constitutes a series of vertical concrete panels cast in individual consecutive slots, made in such a way that each slot intersects the cross-section of the adjacent previously formed vertical panel. A first series of slots are first excavated and at the same time the soil is removed from these slots and it is replaced with a thixotropic fluid after the slot has been excavated. A vertical flexible membrane is inserted in at least one end of the slot, the concrete is then poured into the slot leaving half the vertical membrane within the concrete panel. The spaces between the slots are then excavated and the second series of concrete panels poured surrounding the exposed half of the flexible membrane. Thus between each concrete panel there is a flexible membrane to stop water leaking through the wall.

United States Patent [191 Piecagli 1 Mar. 12, 1974 METHOD FOR THE CONSTRUCTION OF IMPERMEABLE WALLS Primary Examiner.Mervin Stein Assistant Examiner-Alex Grosz 76 I t U Pi l' 4511Har L 1 nven or ia ff l ry S n Attorney, Agent, or FzrmFetherstonhaugh & Co.

[22] Filed: Dec. 24, 1971 [57] ABSTRACT Appl. No.: 207,916

US. Cl 61/35, 52/396, 61/59,

A method is disclosed for the construction of an impermeable concrete wall in the ground, the wall constitutes a series of vertical concrete panels cast in individual consecutive slots, made in such a way that each slot intersects the cross-section of the adjacent previously formed vertical panel. A first series of slots are first excavated and at the same time the soil is removed from these slots and it is replaced with a thixotropic fluid after the slot has been excavated. A vertical flexible membrane is inserted in at least one end of the slot, the concrete is then poured into the slot leaving half the vertical membrane within the concrete panel. The spaces between the slots are then excavated and the second series of concrete panels poured surrounding the exposed half of the flexible membrane. Thus between each concrete panel there is a -flexible membrane to stop water leaking through the wall.

6 Claims, 9 Drawing Figures PATENTEDIAR 12 m4 SHEET .1 [If 5 PATENTEDIAR 12 mm SHEET 2 UF 5 F/GZ PATENTEDIIAR 2 m4 SHEET 3 BF 5 Fla.

PATENTEDIIARIZ m4 37961354 saw u or 5 I HEW PAIENTEBIAR 12 m4 3396354 sum 5 or 5 METHOD FOR THE CONSTRUCTION OF IMPERMEABLE WALLS The present invention relates to a method for constructing a concrete wall in the ground and more particularly a method for forming impermeable partition walls in the ground, the wall constituting a series of vertical concrete panels cast in individual consecutive slots, made in such a way that each slot intersects the cross-section of the adjacent previously formed vertical panel.

A method of digging slots or trenches having vertical walls by the use of thixotropic clay is known. The method consists essentially in that after the proposed line of the slot has'been indicated on the ground with the aid of any known means, the earth is removed from beneath the line by a toothed grab, a chisel or some other means, to the exact width of the slot. The grab displaces the earth in the slot and this is constantly refilled with a liquid thixotropic clay mixture so that the slot is constantly full. After the slot has been dug the required width, depth and length it may then be filled with concrete. This is done by inserting what is referred to as a tremie pipe into the slot so that the bottom of the pipe is at the bottom of the slot and then pouring concrete through the tremie pipe into the slot. As the concrete is poured into the slot, the tremie pipe is slowly raised, so the end of the pipe is just below the level of the liquid concrete. Thus the'thixotropic clay, which is considerably less dense than liquid concrete, is displaced and is generally pumped out of the slot to avoid the clay pouring over the ground. Once the slot has been filled, the concrete is allowed to set to form a first concrete panel, and a second slot is dug adjacent and in line with the first slot using the same procedure of replacing the displaced earth with thixotropic clay. Following this step the tremie pipe is again inserted into the new slot, concrete is poured'into the slotdisplacing .the thixotropic clay to form a second concrete panel,

and you thus have two panels which are joined into one to form a wall. In effect this procedure is generally carried out by digging a seriesof slots spaced apart at a predetermined distance pouring concrete into these slots to form panels and subsequently moving the earth from the space between the first dug slots and then filling these spaces with concrete to form a continuous wall.

In another method of pouring concrete panels in staggered slots in the ground, the slots are'first excavated preferably by means of a chisel similar to that shown in Canadian Pat. No. 671,872 or in the case of soft sandy soil, a toothed grab similar to that shown in Applicant's Canadian application Ser. No. 092,867 filed Sept. 10, 1970. Then shoulder pipes, which are round steel pipes having a diameter approximately the same as the width of the slot are lowered into either one or both ends of the slot so that they stand vertically. Concrete is poured into the slot through the tremie pipe to form a panel and the shoulder pipes are then removed as the concrete hardens. The removal of these steel pipes is a tricky operation and involves raising the pipe slowly as the concrete sets in the slot. After the pipe has been removed, the end face of the concrete panel is curved to the circumference of the pipe. When the adjacent slot is dug and the next concrete panel formed, the join between the panels is curved rather than straight, resulting in a structurally stronger inter locking joint. The shoulder pipe need not necessarily be a pipe, but may be any rolled steel section or may be fabricated from plate. In some instances the shoulder pipe or steel section is left in the slot to strengthen the concrete wall.

One of the problems that can occur with this type of wall construction is leakage or seepage through the joints between the concrete panels. This leakage occurs with straight joints or curved joints made by the shoulder pipe method. The reason for the leakage may be due to a layer of thixotropic clay between the panels or to pockets of sand or soil which stay in the slot and stop the concrete forming a bond or seal therein. Various methods of forming a sea] at this joint have been tried, none have proved completely successful.

It is an object of the present invention-to provide a method for forming an impermeable concrete wall in the ground.

It is'a further object to provide a method of inserting a water tight flexible membrane between the first and second elements of a concrete wall in the ground.

These and other objects will become apparent by referring to the present invention which provides a method for the construction of an impermeable concrete wall in the ground comprising the steps of: excavating a first series of slots at a predetermined length, width and depth along a predetermined line of any desired shape, the first series having spaces of predetermined length between each slot, at the same time removing soil from the slots and replacing the soil with a thixotropic fluid, inserting vertical flexible membranes in at least one end of the first series of slots for their full depth adjacent the spaces, filling the first series of slots with concrete to form first concrete panels such that approximately half the cross-sections of each of the vertical membranes are within the first concrete panels, excavating the soil from the spaces to form a second series of slots and at the same time replacing the soil with thixotropic fluid, filling the second series of slots with concrete to form second concrete panels such that at least one end of the second concrete panels abutts at least one end of the first concrete panels and the remaining half of the cross-sections of each of the flexible membranes are within the second concrete panels.

In drawings which illustrate embodiments of the invention:

FIG. 1 is perspective view showing a flexible membrane of the present invention, attached by clips to a steel support frame.

FIGS. 2, 3, 4, 5, 6 and 7 are top plan diagrammatic views illustrating flexible membranes supported by different embodiments of support frames located at one end of a slot, one .half of the flexible membrane being within the first concrete panel.

FIG. 8 is a perspective view showing a further embodiment of a support frame for a flexible membrane.

FIG. -9 is a perspective view showing another embodi-' ment of a removable clip for attaching a flexible mem-. brane to a support frame similar to that shown in FIG. 1.

In the construction of a concrete wall according to the present invention, the line of the required concretewall is generally laid out on the ground and the decision determining how many slots required is made. In this manner the length of each slot is measured, together with the width. The excavation itself is carried out by a number of ways such as an excavating shovel or a chisel. Methods of excavation depend on the consistency of the ground, if soft or sandy ground is present then a toothed grab or clam shell bucket is used, frequently with a suction hose, to suck out the sand as it is replaced with the thixotropic fluid. If it is rock or hard ground then the excavation is achieved by chiselling'and sucking out the excavated rock or flakes of rock as they come to the surface of the thixotropic clay in the excavation.

As the soil, earth, or rock is removed from the slot it is replaced by thixotropic fluid. The soil, earth or rock tends to float to the top of this fluid where it is removed by a suction pipe and passed through a filter mechanism to separate it from the thixotropic clay which is then returned to the trench.

After the slot has reached the required depth and before the concrete is poured, it is necessary to place the flexible membrane in position at one end or both ends of the slot. This is preferably achieved by taking the flexible membrane and supporting it on a support frame similar to those shown in the drawings. In the embodiment shown in FIG. 1, a flexible membrane is attached to a steel channel 11 by two clips 12 and 13 so that the membrane 10 rests against an outside face 14 of one flange of the channel 11.

The flexible membrane is generally made from rubber however flexible synthetic materials such as plastics are also suitable. The membrane is preferably in the order of half an inch thick, and generally 8 to 12 inches long. The maximum movement that occurs between panels does not generally exceed one quarter inch. FIG. 2 shows a membrane 10 and a supporting frame 11 similar to that shown in FIG. I inserted into one end of a first slot 15. A first concrete panel 16 is poured into the slot 15 using a tremie pipe so that the concrete enters the slot 15 below the thixotropic fluid. As the concrete is poured in, the tremie pipe is slowly raised, and the thixotropic fluid is pumped out at the same rate the concrete is poured into the excavation so the top level of the thixotropic fluid remains constant. When the concrete commences to harden, the supporting channel 11 is slowly withdrawn vertically from the first slot 15. As the concrete has been poured at the bottom of the slot 15 first, it tends to harden at the bottom first, therefore the channel 11 is withdrawn very slowly allowing the concrete to harden up the height of the concrete panel 16 at approximately the same rate as the channel 11 is raised leaving the flexible membrane 10 in place. The removal of the channel 11 is a very tricky operation, if the channel is removed too soon, the concrete will not have hardened sufficiently and it will fall into the space in the slot 15 left by the channel 11. Alternately if the channel 11 is left in place too long the concrete tends to bond to the channel 11, and then cannot be removed at all. In some instances, either on purpose or otherwise, the channel 11 is left in the slot 15, and this forms a supporting structure in the concrete wall. However in a situation when it is planned to leave the support frame in the slot, it usually takes another shape thanthe channel 11 shown in FIG. 2. The next step involved in constructing the wall is to excavate the second slot 17 adjacent to the first concrete panel 16. This is done by methods previously described for excavating the first slot 15. A second concrete panel is poured in this second slot 17 by the same manner in which the first concrete panel 15 was poured, so

that the resulting joint between the first concrete panel 16 and the second concretepanel has the flexible membrane 10 between the two. As this flexible membrane 10 extends into both ends of the adjacent concrete panels, it acts as a complete waterproof seal.

FIG. 3 shows a flexible membrane 20 supported between a first channel 21- and a second channel 22. The two channels have a spacer 23 located between the tips of the adjacent flanges of the channels 21 and 22 so that no pressure occurs from either channel on the membrane 20. In this construction of support frame, the membrane 20 is located in the centre of the slot 24 so that on completion of the first concrete panel 25, one half of the cross-section of the membrane 20 is completely surrounded by concrete. The structural frame may be removed after the first concrete panel 25 has been poured or it may be left in this location to form reinforcing in the concrete wall.

A shoulder pipe 26 is shown in FIG.'4 having an aperture 27 facing in the direction of the first slot 28. The aperture 27 has two lips 29 and is wide enough to allow a flexible membrane 30 to slide in the aperture 27 between the lips 29. The flexible membrane 30 is shown having two bulbous ends 31 to allow the concrete panels to grip the membrane 30. In this configuration, the shoulder pipe 26 with the membrane 30 in place is inserted into the first slot 28 after it has been excavated. The membrane 30 extends to the bottom of the slot 28. A first concrete panel 32 is then poured and this firmly grips the portion of the membrane 30 exposed to the concrete. The shoulder pipe 26 is slowly removedverti' cally from the slot 28 after the concrete has commenced to harden and the second slot 33 adjoining the first concrete panel 32 is excavated in preparation for pouring a second concrete panel. After the second concrete panel has been poured, the joint between the first concrete panel 32 and the second concrete panel is curved in shape to produce a strong connection, and the two bulbous ends 31 of the flexible membrane 30 join the panels together and act as a water seal to stop water passing through the joint.

FIGS. 5 and 6 show further embodiments of shoulder type pipes where the pipes are not round but in the case of FIG. 5 are square and in the case of FIG. 6 are sloped back so that the joint between the two concrete panels is not straight across.

FIG. 7 and FIG. 8 show another frame 40 for supporting a flexible membrane 41. The frame is made from two Z-rolled steel sections 42 with a space 43 therebetween for the web of the membrane 41 to slide freely. The two Z sections 42 are held apart by means of a series of spacer bars 44 spaced down the length of the Z sections 42. The spacer bars 44 are welded to the outside flange of the Z sections 42 and have support plates 45 between'the spacer bars 44 and the centre web of the Z sections '42 to add ridgidity to the two Z sections 42 and retain the space 43 between these Z sections 42 at the correct distance. The method of inserting the membrane 41 is similar to that described for FIGS. 2 and 3. The flexible membrane 41 is not held by the frame 40, thus after the first concrete panel 46 has been poured the frame 40 may be slowly withdrawn leaving the flexible membrane surrounded by the concrete.

FIG. 9 shows a channel frame 50 similar to the type shown in FIGS. 1 and 2. The frame, however, has a special device for holding the flexible membrane 51 to the one flange of the channels 50, with a small hook 53 welded to the flange of the channel frame 50 adjacent the flexible membrane 51. The hook 53 fits into a strap attachment 54 which is attached to the flexible membrane 51. Thus when the channel frame 50 is raised relative to the flexible membrane 51, the hook 53 is lifted out of the strap 54 and the channel frame 50 may be removed leaving the flexible membrane 51 in place.

While several methods of locating the flexible membrane in the first slot have been illustrated in some detail herein, it will be appreciated by those skilled in the art that many variations can be accomplished without departing from the spirit of the present invention, and

that the scope of this invention should be limited only by the scope of the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for the construction of an impermeable concrete wall in the ground, comprising the steps of excavating a first series of slots of predetermined length, width and depth along a predetermined line and of any desired shape, the first series having spaces of predetermined length between each slot, at the same time removing soil from the slots and replacing the soil with a thixotropic fluid, inserting vertical membranes in at least one end of the first series of slots with concrete to form first concrete panels such that approximately half the cross-sections of each of the vertical membranes are within the first concrete panels, excavating the soil from the spaces to form a second series of slots, and at the same time replacing the soil with thixotropic fluid, filling the second series of slots with concrete to form second concrete panels such that at least one end of the second concrete panels abuts atleast one end of the first concrete panels and the remaining half of the cross-sections of each of the flexible membranes are within the second concrete panels, the method being further characterized in that during the pouring of the trixothropic fluid and subsequently the concrete, the

frame 50. This device includes a square aperture 52 in membrane is supported by a steel frame bordering the end of the slot, the steel frame engaging the membrane with at least one rigid vertical edge which supports the membrane in a vertical position and slides freely vertically relative thereto so that it supports the membrane where it engages it regardless of its vertical position relative to the membrane, and including the step of removing the steel frame gradually as the concrete starts to harden at its lower end, and at essentially the same vertical rate as the concrete hardens from the bottom upwardly so that the bottom of the steel frame gradually moves above concrete hard enough to be selfsupporting but not sufficiently hard to bond to the steel frame, the steel frame moving slidably along and still supporting the vertical membrane as it moves upwardly therealong.

2. The method according to claim 1 wherein the steel frame comprises a channel with a width extending across the face of the slots and the vertical flexible membranes are attached to one flange of the channel resulting in the membranes being positioned at one side of the first concrete panels,

3. The method according to claim 1 wherein the steel frames support the flexible membranes so that they are located in the centre of the width of the concrete panels.

4. The method according to claim 1 wherein the steel frame comprises a shoulder pipe having two lips and an aperture therebetween to support a flexible membrane,

the shoulder pipe being inserted into at least one end i of the slot with the aperture facing the excavation.

5. The method according to claim 1 which is further characterized in that said vertical flexible membranes have bulbous opposite side edges which become embedded in the concrete panels.

6. The method according to claim 1 which is further characterized in that said steel frame is a round pipe provided at one side thereof with a pair of spaced longitudinal lips between which the flexible membrane is received. 

1. A method for the construction of an impermeable concrete wall in the ground, comprising the steps of excavating a first series of slots of predetermined length, width and depth along a predetermined line and of any desired shape, the first series having spaces of predetermined length between each slot, at the same time removing soil from the slots and replacing the soil with a thixotropic fluid, inserting vertical membranes in at least one end of the first series of slots with concrete to form first concrete panels such that approximately half the crosssections of each of the vertical membranes are within the first concrete panels, excavating the soil from the spaces to form a second series of slots, and at the same time replacing the soil with thixotropic fluid, filling the second series of slots with concrete to form second concrete panels such that at least one end of the second concrete panels abuts at least one end of the first concrete panels and the remaining half of the crosssections of each of the flexible membranes are within the second concrete panels, the method being further characterized in that during the pouring of the trixothropic fluid and subsequently the concrete, the membrane is supported by a steel frame bordering the end of the slot, the steel frame engaging the membrane with at least one rigid vertical edge which supports the membrane in a vertical position and slides freely vertically relative thereto so that it supports the membrane where it engages it regardless of its vertical position relative to the membrane, and including the step of removing the steel frame gradually as the concrete starts to harden at its lower end, and at essentially the same vertical rate as the concrete hardens from the bottom upwardly so that the bottom of the steel frame gradually moves above concrete hard enough to be self-supporting but not sufficiently hard to bond to the steel frame, the steel frame moving slidably along and still supporting the vertical membrane as it moves upwardly therealong.
 2. The method according to claim 1 wherein the steel frame comprises a channel with a width extending across the face of the slots and the vertical flexible membranes are attached to one flange of the channel resulting in the membranes being positioned at one side of the first concrete panels.
 3. The method according to claim 1 wherein the steel frames support the flexible membranes so that they are located in the centre of the width of the concrete panels.
 4. The method according to claim 1 wherein the steel frame comprises a shoulder pipe having two lips and an aperture therebetween to support a flexible membrane, the shoulder pipe being inserted into at least one end of the slot with the aperture facing the excavation.
 5. The method according to claim 1 which is further characterized in that said vertical flexible membranes have bulbous opposite side edges which become embedded in the concrete panels.
 6. The method according to claim 1 which is further characterized in that said steel frame is a round pipe provided at one side thereof with a pair of spaced longitudinal lips between which the flexible membrane is received. 